Currently in the field of wireless networks, the wireless local area network (WLAN) develops rapidly and there are growing application requirements of the WLAN. The Institute of Electrical and Electronic Engineers (IEEE) industry specification IEEE802.11 group has defined a series of the most common WLAN technologies such as the 802.11a, 802.11b, and 802.11g standards, and subsequently other task groups have appeared and are dedicated to developing improved standards related to the existing 802.11 technology. Wherein, the 802.11ah task group mainly develops WLAN air interface standards using the license-free frequency band under the 1 GHz to support new network applications such as smart grid and sensor networks.
The basic structure of the wireless local access network refers to one Basic Service Set (called BSS), comprising one access point (called AP) and multiple stations (STA) associated with the AP. The 802.11 defines two operating modes: Distributed Coordination Function (DCF) and Point Coordination Function (PCF), as well as improvements on the two operating modes: Enhanced Distributed Coordination Access (EDCA) function and Hybrid Coordination Function Controlled Channel Access (HCFCCA) function. Wherein, the DCF is the most basic operating mode that uses the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism to make a plurality of stations share a radio channel. The EDCA function is the enhanced operating mode based on the CSMA/CA mechanism, supporting a plurality of different priority queues sharing the radio channel, and it uses transmission opportunity (called TXOP) as the unit to transmit data of each priority queue.
Using the license-free frequency band resources under 1 GHz can support communications in a wider range. However, the transmission time of the Physical Protocol Data Unit (PPDU) in the station in the BSS boundary will increase, it needs more power consumption, the battery life of the station is limited, and the replacement cycle is relatively long, meanwhile, in order to reduce the network complexity, it was proposed in the 802.11ah that it needs to support up to two-hop relay, namely, three-layer network architecture: root access point (Rt-AP), relay, and STA. The architectural structure is shown in FIG. 1. The relay is composed of two functional entities, wherein the first functional entity (Relay-STA (R-STA)) and the second functional entity (Rt-AP) are in the same BSS, namely, BSS1; the Relay-AP (R-AP) and the STA are in another BSS, namely, BSS2.
For the energy saving of the station, reducing the transmission delay of data packets, making the station forward or receive data as soon as possible, the transmission opportunity sharing which is used in the relay is proposed, as shown in FIG. 2. In the transmission opportunity sharing of the relay, when the relay acknowledges data of the AP, there are two acknowledgement methods: explicit acknowledgement and implicit acknowledgment. The explicit acknowledgement refers to acknowledging the data sent by the AP with a single acknowledgment frame, as shown in FIG. 2; the implicit acknowledgment refers to using an implicit acknowledgment for the data sent by the AP, and the implicit acknowledgment is contained in the data sent by the relay to the STA, as shown in FIG. 3. When the STA sends uplink data to the AP via the relay, the same scheme may also be used.
The abovementioned scheme is applicable to one frame transmission, but after the AP or STA obtains the channel by competition, when there are multiple frames to be transmitted and there is one frame to be transmitted to the relay, then the control right of channel is not at the party which obtains the channel by competition but is controlled by the relay, which is not conducive to the party obtaining the channel by competition to control the channel and the subsequent frame transmission. The AP or the STA may have a plurality of frames to be transmitted to the relay, then it needs to control the channel, which will contradict the idea that the relay can freely control the channel obtained by the AP or STA through competition.
In summary, in the existing transmission opportunity sharing mechanism, there is no method for effectively managing the control right of channel, which increase the data transmission delay and affects the data transmission efficiency.